French Pat. No. 2,227,332 describes a method of heat treatment for armoured electric components with mineral isulants surrounded by stainless steel sheaths. The treatment is performed on a blank as it passes between two successive drawing operations, said method being divided into three consecutive steps: annealing the sheaths by high-frequency heating, annealing the cores of the cable in a thermally controlled chamber, heat being transmitted from the sheaths to the cores (together with an optional, additional supply of heat) and lastly, quenching the sheaths and the cores by a flow of water coming into contact with the sheaths.
While such a method which is very suitable for annealing and quenching long metal components made of steel with a well-defined austenitic structure, it is difficult to adapt to annealing and quenching metal components made of steel with slightly differing austenitic structures or of variable diameter or thickness. Sometimes, insufficient quenching of the steel is observed which leads to the appearance at some points of ferritic structures or to the appearance of unusual crystal enlargement which reduces the mechanical characteristics and can cause breakages during subsequent mechanical treatment.
Preferred implementations of the present invention mitigate these drawbacks by annealing and quenching such long metal components while making adjustments according to the quality of the steel, its diameter and its thickness, thereby avoiding the danger of either a ferritic structure or unusually large crystals appearing.